An example of a Z decay into two electrons. In the track detector in the centre we see a track from each electron (one green and one red) going in 180 degrees from each other. In the EM-calorimeter a bit further out, two big energy depositions are visible as boxes. Note that the size of the box only shows the amount of the energy of the detected particle, not how far the particle moved in the detector.
Other important characteristics for electron events are that there are only two tracks and that almost all energy is detected, as seen above the picture of the collision.